Field of Invention
This invention relates to an improved design for a linear construction truss and a method of manufacturing said linear construction truss.
Prior Art
There are many designs for linear members (beams and trusses) used in construction. Such linear members have to be resistant to shear stress and bending, since the loads on them are typically perpendicular to the axis of the linear member. The I-beam is one example of such a linear member. While the I-beam is an efficient design in that it concentrates the material where the largest linear stress is bound to occur, the manufacturing process for making I-beams involves hot rolling, which is very energy-intensive and environmentally damaging; furthermore, steel I-beams are relatively heavy.
Another possible type of design for a linear member is a hollow sheet metal box beam, such as the one described in U.S. Pat. No. 2,007,898 to Ragsdale. Ragsdale discloses a hollow sheet metal beam with a generally rectangular cross section. While such beams are lightweight and do not require energy-intensive hot rolling methods to construct, a beam with a hollow cross-section is not very strong, and susceptible to buckling.
Due to the advantages offered by a sheet metal construction over an I-beam or a lumber beam, many attempts have been made to reinforce a hollow sheet metal beam from the inside. One such design for a reinforced hollow sheet metal beam is disclosed in U.S. Pat. No. 3,783,498 to Moyer (shown in FIG. 1). Moyer discloses a beam with a hexagonal cross-section, made of sheet metal and welded. The beam is reinforced at two of its vertical sides with sheet metal strips welded to those two sides. These strips provide extra strength on the sides that bear the most stress. However, due to the fact that the horizontal sides are not reinforced and that there is no reinforcing elements on the interior of the beam, the resulting linear member is still not strong enough for some purposes.
Another method of reinforcing the interior of a hollow sheet metal beam is disclosed in U.S. Pat. No. 4,023,683 to Vargo. Vargo discloses reinforcing the interior of a hollow sheet metal beam with one or more planar webs. While that design is stronger than a simple hollow sheet metal beam, it is still not strong enough for some construction applications. One of the reasons for its relative lack of strength is that the planar webs are aligned with the axis of the beam, which increases the strain on these webs in normal operation.